Multi-axis sensor

ABSTRACT

A sensor strain causer can be made into a simple shape, and the attachment work for strain gauges is made easy. In a multiaxial sensor  1  for measuring one or more of multiaxial force, moment, acceleration, and angular acceleration, externally applied, a plurality of strain gauges R 11  to R 48  disposed on one plane are provided. Thereby, because the time for the attachment work for the strain gauges R 11  to R 48  can be shortened, the mass productivity can be improved and the cost can be reduced.

TECHNICAL FIELD

The present invention relates to a multiaxial sensor capable ofmeasuring at least one of multiaxial force, moment, acceleration, andangular velocity, externally applied to a first member and a secondmember.

BACKGROUND ART

As shown in FIG. 49, Patent Document 1 discloses a force-moment sensor103 comprising a first member 100 and a second member 101 provided as apair of opposed circular plates; annular bridge elements 102 connectingthe first and second members 100 and 101 to each other; and a straingauge attached to each bridge element 102.

In the sensor 103, each bridge element 102 is disposed perpendicularlyto the first and second members 100 and 101. A strain gauge is attachedwith an adhesive to the outer circumferential surface of each bridgeelement 102 or the inner surface of a hole 104. A force or momentapplied between the first and second members 100 and 101 is calculatedby detecting the direction and magnitude of the strain of the annularshape of each bridge element 102 caused by the force or moment.

Patent Document: JP-A-63-78032 (FIG. 1; page 5, lower right column, line12 to page 6, upper left column, line 14; and page 7, upper left column,line 20 to upper right column, line 12)

DISCLOSURE OF THE INVENTION

Problem that the Invention is to Solve

In the technique disclosed in Patent Document 1, each bridge element 102as a sensor strain causer to which a strain gauge is attached, has acomplicated three-dimensional shape. This causes an increase in cost forassembling and processing the first and second members 100 and 101 andthe bridge elements 102. In addition, because each strain gauge must bethree-dimensionally attached to a curved surface or the like of a bridgeelement 102, this brings about an increase in time for the attachmentwork, deterioration of mass productivity, and an increase in cost.

An object of the present invention is to provide a multiaxial sensor inwhich a sensor strain causer can be made into a simple shape and theattachment work for a strain gauge can be made easy.

Means for Solving the Problem and the Effect of the Invention

A multiaxial sensor of the present invention is for measuring one ormore of multiaxial force, moment, acceleration, and angularacceleration, externally applied, and comprises a plurality of straingauges disposed on one plane.

According to this feature, because the strain gauges are disposed on oneplane, the time for the attachment work can be shortened in comparisonwith a conventional case wherein the strain gauges arethree-dimensionally attached to a curved surface or the like of a bridgeelement. Therefore, the mass productivity can be improved and the costcan be reduced.

The multiaxial sensor of the present invention may further comprise afirst diaphragm to which the plurality of strain gauges are attached.According to this feature, because the sensor strain causer to which thestrain gauges are attached is simple in shape, the cost for assemblingthe multiaxial sensor can be reduced.

In the multiaxial sensor of the present invention, first diaphragms maybe arranged around a central point of the plane at regular angularintervals and at the same distance from the central point. According tothis feature, a multiaxial force, moment, acceleration, or angularacceleration, can be calculated by a relatively easy calculation fromchanges in the resistance values of the strain gauges of each firstdiaphragm.

In the multiaxial sensor of the present invention, the angular intervalmay be 90 degrees. According to this feature, forces, moments,accelerations, or angular accelerations, on the X and Y axes ofCartesian coordinates with its origin being set at the central point ofthe plane, can be easily calculated.

In the multiaxial sensor of the present invention, the diaphragms may bedisposed in positive and negative directions on X and Y axes with anorigin being defined at the central point. According to this feature,forces, moments, accelerations, or angular accelerations, on the X and Yaxes, can be very easily calculated.

In the multiaxial sensor of the present invention, the angular intervalmay be 120 degrees. According to this feature, because multiaxialforces, moments, accelerations, or angular accelerations, can becalculated on three first diaphragms, the construction of the multiaxialsensor can be further simplified.

In the multiaxial sensor of the present invention, a thin portion ofeach first diaphragm may be annular and provided with eight straingauges, and the strain gauges may be disposed at outer and inner edgeportions of the first diaphragm on a line extending between a centralpoint of the first diaphragm and the central point of the plane, and atouter and inner edge portions of the first diaphragm on a lineperpendicular to the former line at the central point of the firstdiaphragm. According to this feature, because the strain gauges can beattached to portions of the first diaphragm where the largest strainsare generated, the sensitivity can be improved.

The multiaxial sensor of the present invention may further comprise anoperative body provided on a central portion of the first diaphragm, formeasuring multiaxial accelerations and angular accelerations applied tothe multiaxial sensor. According to this feature, when an accelerationis applied to the multiaxial sensor, an inertial force acts on theoperative body. Thus, the operative body is displaced and a strain isgenerated in the first diaphragm. By detecting the strain of the firstdiaphragm, multiaxial accelerations and angular accelerations can bemeasured.

The multiaxial sensor of the present invention may further comprise afirst member comprising the first diaphragm; a second member comprisinga second diaphragm opposed to the first diaphragm and provided with nostrain gauges; and a connecting shaft connecting the opposed first andsecond diaphragms, for measuring multiaxial forces and moments appliedbetween the first and second members. According to this feature,multiaxial forces and moments can be measured with the strain gaugesattached on only one plane.

The multiaxial sensor of the present invention may further comprise afirst member comprising the first diaphragm; a second member comprisinga second diaphragm opposed to the first diaphragm and provided with aplurality of strain gauges disposed on one plane, and a connecting shaftconnecting the opposed first and second diaphragms, for measuringmultiaxial forces and moments applied between the first and secondmembers. According to this feature, because there are independent twogroups of electric signals indicating components of the same force ormoment, the sensor outputs can be doubled to intend to make the accuracyhigher.

In the multiaxial sensor of the present invention, the strain gauges ofthe first member and the strain gauges of the second member may bedisposed symmetrically with respect to a barycentric point of themultiaxial sensor. According to this feature, because two groups ofelectric signals can be equally treated, the accuracy is furtherimproved.

In the multiaxial sensor of the present invention, either outputs of thestrain gauges of the first member and the strain gauges of the secondmember may be adopted if the other outputs are out of a predeterminedrange. According to this feature, even if either strain gauges becomeabnormal by some cause, the multiaxial sensor can continue to be used byusing the other strain gauges. Thus, a very highly reliable controlsystem can be constructed.

In the multiaxial sensor of the present invention, only one diaphragmmay be disposed on the plane. According to this feature, because aplurality of first diaphragms need not be provided on one plane, themultiaxial sensor can be reduced in size. In addition, because the shapeof the multiaxial sensor is simplified, the cost required for cuttingcan be reduced.

The multiaxial sensor of the present invention may further compriseoperative bodies being in contact with the first diaphragms at positionsarranged around the central point of the plane at regular angularintervals and at the same distance from the central point, for measuringmultiaxial accelerations and angular accelerations applied to themultiaxial sensor. According to this feature, when an acceleration isapplied to the multiaxial sensor, an inertial force acts on eachoperative body. Thus, the operative body is displaced and a strain isgenerated in the first diaphragm. By detecting the strain of the firstdiaphragm, multiaxial accelerations and angular accelerations can bemeasured.

The multiaxial sensor of the present invention may further comprise afirst member comprising the first diaphragm; a second member comprisingonly one second diaphragm provided with no strain gauges; and operativebodies connecting the first and second diaphragms; the first and secondmembers may be disposed so that a central point of the first diaphragmof the first member is opposed to a central point of the seconddiaphragm of the second member; and the operative bodies may connect thefirst and second diaphragms at positions arranged around the centralpoints of the first and second diaphragms at regular angular intervalsand at the same distance from the central points, for measuringmultiaxial forces and moments applied between the first and secondmembers. According to this feature, multiaxial forces and moments can bemeasured with the strain gauges attached on only one plane.

The multiaxial sensor of the present invention may further comprise afirst member comprising the first diaphragm; a second member comprisinga second diaphragm provided with a plurality of strain gauges disposedon one plane; and operative bodies connecting the first and seconddiaphragms; the first and second members may be disposed so that acentral point of the first diaphragm of the first member is opposed to acentral point of the second diaphragm of the second member; and theoperative bodies may connect the first and second diaphragms atpositions arranged around the central points of the first and seconddiaphragms at regular angular intervals and at the same distance fromthe central points, for measuring multiaxial forces and moments appliedbetween the first and second members. According to this feature, becausethere are independent two groups of electric signals indicatingcomponents of the same force or moment, the sensor outputs can bedoubled to intend to make the accuracy higher.

In the multiaxial sensor of the present invention, the strain gauges ofthe first member and the strain gauges of the second member may bedisposed symmetrically with respect to a barycentric point of themultiaxial sensor. According to this feature, because two groups ofelectric signals can be equally treated, the accuracy is furtherimproved.

In the multiaxial sensor of the present invention, either outputs of thestrain gauges of the first member and the strain gauges of the secondmember are adopted if the other outputs are out of a predeterminedrange. According to this feature, even if either strain gauges becomeabnormal by some cause, the multiaxial sensor can continue to be used byusing the other strain gauges. Thus, a very highly reliable controlsystem can be constructed.

In the multiaxial sensor of the present invention, the angular intervalmay be 90 degrees. According to this feature, forces, moments,accelerations, or angular accelerations, on the X and Y axes ofCartesian coordinates with its origin being set at the central point ofthe first diaphragm, can be easily calculated.

In the multiaxial sensor of the present invention, the operative bodiesmay be disposed in positive and negative directions on X and Y axes withan origin being defined at the central point of the first diaphragm.According to this feature, forces, moments, accelerations, or angularaccelerations, on the X and Y axes of Cartesian coordinates with itsorigin being set at the central point of the first diaphragm, can beeasily calculated.

In the multiaxial sensor of the present invention, the angular intervalmay be 120 degrees. According to this feature, because multiaxialforces, moments, accelerations, or angular accelerations, can becalculated on three operative bodies formed on the first diaphragm, theconstruction of the multiaxial sensor can be further simplified.

In the multiaxial sensor of the present invention, the strain gauges maybe disposed at edge portions of the operative bodies on a line extendingbetween a central point of a portion on the plane corresponding to theoperative bodies, and the central point of the first diaphragm; at edgeportions of the operative bodies on a line perpendicular to the formerline at the central point of the portion on the plane corresponding tothe operative bodies; and at either of edge portions of the operativebodies and edge portions of the first diaphragm, at positions arrangedaround the central point of the first diaphragm at regular angularintervals and at the same distance from the central point. According tothis feature, because the strain gauges can be attached to portions ofthe first diaphragm where the largest strains are generated, thesensitivity can be improved. In addition, multiaxial forces, moments,accelerations, or angular accelerations, can be calculated with lessstrain gauges in comparison with a case wherein a plurality of firstdiaphragms are provided on one plane. Thus, the cost for the straingauges and the cost for wiring can be reduced.

In the multiaxial sensor of the present invention, each of the straingauges may be made of a piezoresistance element. According to thisfeature, because the piezoresistance element is ten times or more higherin gauge factor than a foil strain gauge, the sensitivity can beimproved ten times or more in comparison with a case wherein the foilstrain gauge is used.

In the multiaxial sensor of the present invention, each of the straingauges may be made of a thin film of chromium oxide formed on aninsulating film. According to this feature, because the gauge is tentimes or more higher in gauge factor than a general foil strain gauge,the sensitivity can be improved ten times or more in comparison with acase wherein such a general foil strain gauge is used.

BEST FORM FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to drawings. FIG. 1A is a plan view showing thearrangement of strain gauges when a multiaxial sensor 1 according to afirst embodiment of the present invention is Z-axially transparentlyviewed from the position of a second member 3. FIG. 1B is a centralvertical sectional front view of the multiaxial sensor 1. The multiaxialsensor 1 is for measuring one of multiaxial force, moment, acceleration,and angular acceleration, externally applied to a first member 2 and asecond member 3. The multiaxial sensor 1 has therein a plurality ofstrain gauges R11 to R48 disposed on one plane. Each of the first andsecond members 2 and 3 is made into a disk-shaped flange. The straingauges R11 to R48 are attached only to the front surface 2 a of thefirst member 2.

In this embodiment, an X-Y-Z three-dimensional coordinate system isdefined as a matter of explanatory convenience, and the disposition ofeach component will be described with reference to the coordinatesystem. In FIG. 1B, the origin O is defined at the center of the frontsurface 2 a of the first member 2; the X axis is defined to extendhorizontally rightward; the Y axis is defined to extend frontwardperpendicularly to FIG. 1B; and the Z axis is defined to extendvertically downward. Thus, the front surface 2 a of the first member 2is on the X-Y plane, and the Z axis extends through the center of thefirst member 2.

Each of the first and second members 2 and 3 has four diaphragms 4, 5,6, and 7. The corresponding diaphragms of the first and second members 2and 3 are opposed to each other. Each of the diaphragms 4 to 7 is madeinto a thin portion. A central shaft 8 is formed at the center of eachof the diaphragms 4 to 7. The central shafts 8 of the diaphragms opposedto each other are connected by a bolt 9. Thereby, the first and secondmembers 2 and 3 are united. In each of the diaphragms 4 to 7, the thinportion is annular because of the presence of the central shaft 8.

The diaphragms 4 to 7 of the first member 2 are arranged around theorigin O at regular angular intervals and at the same distance from theorigin O. In this embodiment, they are arranged at angular intervals of90 degrees. The diaphragms 4 to 7 of the first member 2 are disposed atpositive and negative positions on the X and Y axes. The diaphragms 4 to7 of the second member 3 are disposed so as to be opposed to therespective diaphragms 4 to 7 of the first member 2. Thus, the multiaxialsensor 1 functions as a 6-axis force sensor for measuring forces ofperpendicular three axes in three-dimensional space, and moments aroundthe respective axes. FIG. 2 shows the directions of the X, Y, and Zaxes, and the directions of moments Mx, My, and Mz around the respectiveaxes.

Each of the diaphragms 4 to 7 of the first member 2 has thereon eightstrain gauges. As shown in FIG. 1A, the strain gauges R11 to R48 aredisposed at outer and inner edges of the thin portions of the diaphragms4 to 7 along the X and Y axes. Thus, the strain gauges R11 to R48 areattached at where the largest strains are generated in the multiaxialsensor 1. Leads for the strain gauges are omitted in FIG. 1A.

As each of the strain gauges R11 to R48, a metallic foil strain gauge ora metallic wire strain gauge is used. Each of the strain gauges R11 toR48 is a kind of resistor, and a detector used by being attached atwhere strain is generated. Because the resistance value changes bygeneration of strain, the strain epsilon can be measured. In general,such a strain gauge has a proportional characteristic in which theresistance value increases to strain epsilon by tension while theresistance value decreases to strain epsilon by compression. In general,such a strain gauge is used within the elastic region of the material inwhich the stress sigma is proportional to the strain epsilon. Also inthis embodiment, the strain gauges are used within the elastic region ofthe first member 2.

The diaphragms 4 to 7 are the same in size and thickness. Thus, they arethe same in rigidity. Therefore, for example, when the first and secondmembers 2 and 3 are deformed to form four sides of a parallelogram as awhole as shown in FIG. 3, strains corresponding to the directions andmagnitudes of forces are generated on the strain gauges R11 to R48 ofthe diaphragms 4 to 7, and the forces and moments can be detected withhigh accuracy. To simplify the attachment work for the strain gauges orintend to protect the strain gauges, a step may be formed at eachattachment position. A tap hole or holes for attachment to anothermember may be formed at portions other than the diaphragms 4 to 7.Although the first and second members 2 and 3 are united by the centralshafts 8 being connected with the bolt 9, they may be formed directlyfrom one body by cutting, or the central shafts 8 may be connected bywelding.

Next, a principle for detecting a force or moment for each axis will bedescribed. In the below description, it is assumed that the first member2 is fixed and the force or moment is applied to the second member 3.

FIG. 3 shows a state when an X-axial force Fx is applied. In this state,all the diaphragms 4 to 7 of the first and second members 2 and 3 havebeen displaced as shown in FIG. 3, and strains are detected. FIG. 4shows changes in the strain gauges R11 to R48. In FIG. 4, (+) indicatesan increase in resistance value, and (−) indicates a decrease inresistance value. In the strain gauges denoted by neither of thesymbols, their resistance values hardly changed.

Next, the description of a case wherein a Y-axial force Fy is applied isomitted here because it can be understood by sifting by 90 degrees thestate when the X-axial force Fx is applied.

FIG. 5 shows a state of the multiaxial sensor 1 when a Z-axial force Fzis applied. FIG. 6 shows changes in the strain gauges in the state ofFIG. 5.

FIG. 7 shows a state of the multiaxial sensor 1 when an X-axial momentMx is applied. FIG. 8 shows changes in the strain gauges in the state ofFIG. 7.

Next, the description of a case wherein a Y-axial moment My is appliedis omitted here because it can be understood by sifting by 90 degreesthe state when the X-axial moment Mx is applied.

When a Z-axial moment Mz is applied, the second member 3 is rotatedaround the Z axis. FIG. 9 shows changes in the strain gauges in thisstate.

Table 1 shows changes in the strain gauges R11 to R48 to theabove-described forces and moments. In Table 1, + indicates an increasein resistance value; − indicates a decrease in resistance value; and nosymbol indicates that the resistance value hardly changed. In the caseof a force or moment in the reverse direction, the symbol is reversed.

[Table 1] TABLE 1 Force R11 R12 R13 R14 R15 R16 R17 R18 R21 R22 R23 R24R25 R26 R27 R28 Fx − + − + − + − + Fy − + − + − + − + Fz − + + − − + + −− + + − − + + − Mx + − − + + − − + My + − − + + − − + Mz − + − + − + − +Force R31 R32 R33 R34 R35 R36 R37 R38 R41 R42 R43 R44 R45 R46 R47 R48 Fx− + − + − + − + Fy − + − + − + − + Fz − + + − − + + − − + + − − + + − Mx− + + − − + + − My − + + − − + + − Mz + − + − + − + −

Using the above nature, the forces and moments can be detected by thecalculation of Equation 1.Fx=(R22+R42)−(R23+R43)Fy=(R16+R36)−(R17+R37)Fz=(R13+R26+R32+R47)−(R11+R28+R34+R45)Mx=(R25+R46)−(R27+R48)My=(R14+R33)−(R12+R31)Mz=(R18+R24+R35+R41)−(R15+R21+R38+R44)  [Equation 1]

In this calculation, there is no waste because each of the strain gaugesR11 to R48 is used one time, and this calculation is convenient for acase wherein the calculation is carried out by an OP amplifier after theresistances are converted into voltages. In addition, as for Fz and Mz,in which the rigidity increases on the structure to decrease thesensitivity, the sensitivity can be improved because eight straingauges, which is twice the number of strain gauges in the other cases.As a matter of course, the calculation method is not limited to Equation1.

The calculation of Equation 1 may be carried out by an OP amplifierafter the resistance values are converted into voltages by known ornovel means, or carried out by a micro controller or a computer using anAD converter.

Otherwise, a force or moment can be detected by bridge circuitsconstructed as shown in FIG. 10, to which a constant voltage or aconstant current is applied. Further, a force or moment can be detectedeven by half bridges constructed to reduce the number of strain gauges,though not shown. As a matter of course, the combination of straingauges is not limited to that shown in FIG. 10.

In this embodiment, each of the diaphragms 4 to 7 of the first member 2is disposed on the X or Y axis. However, the present invention is notlimited to that. That is, the arrangement directions on the multiaxialsensor 1 having the same construction may be changed so that each of thediaphragms 4 to 7 of the first member 2 is not disposed on any axis. Inthis case, the sensor does not function as a 6-axis sensor, and it is a5-axis sensor. In this embodiment, the multiaxial sensor is used as a6-axis sensor. However, the present invention is not limited to that.For example, the sensor may be used as 2-axis sensor that detects onlyX- and Y-axial forces.

Next, a second embodiment of the present invention will be describedwith reference to FIG. 11. As shown in FIG. 11, in the secondembodiment, a piezoresistance element 10 is used as each strain gauge.Piezoresistance elements 10 necessary for one diaphragm are integratedon one semiconductor Si wafer 11 by using a semiconductor manufacturingprocess, and the wafer is fixed to the diaphragm by die bonding. Such apiezoresistance element 10 is ten times or more higher in gauge factorthan a foil strain gauge. Thus, the sensitivity can be improved tentimes or more in comparison with a case wherein a foil strain gauge isused.

Next, a third embodiment of the present invention will be described withreference to FIG. 12. In the third embodiment, although the constructionof the multiaxial sensor 1 is the same as that of the first embodiment,the construction of each bridge is changed. As shown in FIG. 12, eachbridge is constructed by four strain gauges linearly arranged on each ofthe diaphragms 4 to 7. Thereby, the condition of generation of strain oneach of the diaphragms 4 to 7 can be directly output as eight voltages.

In this case, a force or moment can be calculated by Equation 2.Fx=V4−V2Fy=V3−V1Fz=V5+V6+V7+V8Mx=V8−V6My=V7−V5Mz=V1+V2+V3+V4  [Equation 2]

The calculation of Equation 2 may be carried out by an OP amplifierafter the resistance values are converted into voltages by known ornovel means, or carried out by a micro controller or a computer using anAD converter.

Next, a fourth embodiment of the present invention will be describedwith reference to FIGS. 13 and 14. In the fourth embodiment, the straingauges R11 to R48 are attached to the first member 2 like the firstembodiment, and strain gauges R111 to R148 are attached to the secondmember 3 at positions symmetrical with respect to the barycentric pointO′ as shown in FIG. 13. Because of such mechanical symmetry, when aforce or moment is applied to the multiaxial sensor 1, a symmetricalstrain in accordance with the kind of force is generated in each of thediaphragms 4 to 7. That is, a characteristic feature is utilized thattwo sets of strain gauges R11 to R48 and R111 to R148 can be disposed atsymmetrical positions because strain gauges are disposed on one plane inthe multiaxial sensor 1 of the present invention.

The strain gauges R11 to R48 constitute the same circuits as those shownin FIG. 10 to output voltages Vfx1, Vfy1, Vfz1, Vmx1, Vmy1, and Vmz1corresponding to forces Fx, Fy, and Fz and moments Mx, My, and Mz. Thestrain gauges R111 to R148 also constitute the same circuits as thoseshown in FIG. 10 to output voltages Vfx2, Vfy2, Vfz2, Vmx2, Vmy2, andVmz2 corresponding to forces Fx, Fy, and Fz and moments Mx, My, and Mz.Settings on the circuits have been made so that increases/decreases inthe voltages Vfx1, Vfy1, Vfz1, Vmx1, Vmy1, and Vmz1 coincide withincreases/decreases in the voltages Vfx2, Vfy2, Vfz2, Vmx2, Vmy2, andVmz2 when a force or moment is applied.

As described above, in this embodiment, there are independent two groupsof electric signals indicating components of the same force or moment,thereby intending to double the sensor outputs.

FIG. 14 shows examples of amplifier circuits 12 for amplifying Vfx1,Vfy1, Vfz1, Vmx1, Vmy1, Vmz1, Vfx2, Vfy2, Vfz2, Vmx2, Vmy2, and Vmz2,which are signals of the bridges to detect each force or moment. In thisembodiment, adjustment has been made so that voltage values within therange of 25 to 75% of the power supply voltage can be obtained in therange of the rated load. Further, the amplified outputs are input to ADconverter ports 14 of a micro controller 13.

In general, because a change in the output of a bridge circuitconstituted by strain gauges is very little as several mV, it must beamplified to several hundred times or more by an amplifier or the like.Even when a high-sensitive piezoresistance element 10 is used, theoutput sensitivity is about ten times of that of a metallic foil straingauge. Therefore, if a strain gauge constituting the bridge circuit isbroken by some cause, the balance is disrupted and deviation to thevicinity of the lower or upper limit of the power supply voltage mayoccur.

For this reason, using the feature that the output signals of thesensors have been doubled, the following procedure is carried out asshown in FIG. 14.

Suppose that the lower power supply voltage of the amplifiers is Vee andthe higher one is Vcc. Suppose that a lower voltage that is considerednot to be output by the multiaxial sensor 1 in the range of normal use,is VL, and a larger one is VH. Vee is lower than VL, and VH is lowerthan Vcc. VL and VH are A/D-converted values. VL and VH may bedetermined for each output in accordance with the characteristics of themultiaxial sensor 1.

In the case of the X-axial force Fx, the micro controller judges whetheror not VL is not higher than Vfx1 and Vfx1 is not higher than VH; and VLis not higher than Vfx2 and Vfx2 is not higher than VH, in S1 and S2.When both are within the ranges, that is, Yes in S1 and Yes in S2, thesignal of Vfx1 is preferentially adopted as a control signal, in S3.

If Vfx1 is out of the range, that is, No in S1, it is judged to be anabnormal output, and Vfx2 is checked, in S4. When Vfx2 is within therange, that is, Yes in S2, Vfx2 is processed as the signal of the forceFx in place of Vfx1. If Vfx2 is also out of the range, that is, No inS2, both outputs are judged to be abnormal, and processing for trouble,such as emergency stop, is performed, in S5.

The same process is carried out for a force or moment other than Fx.

According to this embodiment, by doubling the output signal, even if oneoutput is abnormal due to break of a strain gauge, the multiaxial sensor1 can continue to be used by using the other output. Thus, a very highlyreliable control system can be constructed.

Next, a fifth embodiment of the present invention will be described withreference to FIG. 15. FIG. 15 is a plan view showing the arrangement ofstrain gauges R11 to R38 when a multiaxial sensor 1 according to thefifth embodiment is Z-axially transparently viewed from the position ofa second member 3. In the fifth embodiment, each of first and secondmembers 2 and 3 has three diaphragms 4 to 6. The correspondingdiaphragms of the first and second members 2 and 3 are opposed to eachother. This multiaxial sensor 1 is a 6-axis force sensor for measuringforces of perpendicular three axes in three-dimensional space, andmoments around the respective axes.

The diaphragms 4 to 6 of the first member 2 are arranged around theorigin O at regular angular intervals and at the same distance from theorigin O. In this embodiment, they are arranged at angular intervals of120 degrees. The diaphragms 4 to 6 of the second member 3 are disposedso as to be opposed to the respective diaphragms 4 to 6 of the firstmember 2. Each of the diaphragms 4 to 6 of the first member 2 hasthereon eight strain gauges. The strain gauges R11 to R38 are disposedon the front surface of the first member 2 at outer and inner edges ofthe diaphragms 4 to 6 on straight lines extending from the centers ofthe diaphragms 4 to 6 to the origin O, and at outer and inner edges ofthe diaphragms 4 to 6 on straight lines perpendicular to the abovestraight lines at the centers of the diaphragms 4 to 6.

More specifically, the strain gauges R11 to R14 are disposed on asegment OC extending from the origin O so as to form an angle of 120degrees from the Y-axial negative direction to the X-axial positivedirection. The strain gauges R31 to R34 are disposed on a segment ODextending from the origin O so as to form an angle of 120 degrees fromthe Y-axial negative direction to the X-axial negative direction. Thestrain gauges R15 to R18 are disposed perpendicularly to the segment OC.The strain gauges R35 to R38 are disposed perpendicularly to the segmentOD. The strain gauges R21 to R28 are the same as those of the firstembodiment.

Each strain gauge may be a metallic foil strain gauge like the firstembodiment, or a piezoresistance element 10 like the second embodiment.The other construction is the same as that of the first embodiment, andthus the description thereof is omitted.

A principle for detecting a force or moment for each axis according tothis embodiment will be described. In the below description, it isassumed that the first member 2 is fixed and the force or moment isapplied to the second member 3. A strain gauge group constituted by fourstrain gauges arranged on a straight line becomes the highest in rate ofthe change in resistance value and increases in sensitivity to a strainwhen the tensile or compressive strain is applied along the line of thearrangement. As shown in FIG. 15, six strain gauge groups exist, whichdiffer from one another in direction in which the sensitivity increases.However, when the sensitivity of each strain gauge group is consideredby resolving into X-, Y-, and Z-axial vectors, a force or moment having6-axial components can be detected.

Bridge circuits as shown in FIG. 16 are constructed for the straingauges R11 to R38 shown in FIG. 15, and a constant voltage or a constantcurrent is applied to them. Thereby, the strain gauges R15 to R18 candetect as a voltage V1 a force component at 60 degrees from the X-axialpositive direction to the Y-axial negative direction; the strain gaugesR25 to R28 can detect as a voltage V2 a force component at 90 degreesfrom the X-axial positive direction to the Y-axial negative direction;and the strain gauges R35 to R38 can detect as a voltage V3 a forcecomponent at 300 degrees from the X-axial positive direction to theY-axial negative direction. R11 to R14, R25 to R28, and R31 to R34 candetect as V4, V5, and V6 Z-axial forces at the centers of the diaphragms4 to 6, respectively.

When node voltages of the bridge circuits in FIG. 16 are e1 to e12,Equation 3 is obtained.V1=e1−e2V2=e3−e4V3=e5−e6V4=e7−e8V5=e9−e10V2=e11−e12  [Equation 3]

Of them, V1, V2, and V3 can be expressed by Equation 4 by resolving intoX- and Y-axial vectors.V1=(V1X,V1Y)=(V1/2,V1·√{square root over ( )}3/2)V2=(V2X,V2Y)=(V2,0)V3=(V3X,V3Y)=(V3/2,V3·√{square root over ( )}3/2)  [Equation 4]

Therefore, when the X-axial resultant force applied to the second member3 is Fx and the Y-axial resultant force is Fy, they can be detected asin Equation 5.FX=(V1/2)+V2+(V3/2)FY=(V1·√{square root over ( )}3/2)+(V3·√{square root over ()}3/2)  [Equation 5]

FIG. 17 shows a state of displacement of the diaphragm 5 when a Y-axialnegative force Fy is applied. At this time, tensile strains aregenerated on the strain gauges R25 and R27 to increase theirresistances, and compressive strains are generated on the strain gaugesR26 and R28 to decrease their resistances. Strains are scarcelygenerated on the strain gauges R21 to R24 disposed perpendicularly tothe force Fy.

Similar Y-axial displacements and strains are generated in the other twodiaphragms 4 and 6. However, because the lines of the arrangements ofthe strain gauges R11 to R18 and R31 to R38 differ from the X and Yaxes, the changes in the resistance values of the strain gauges differfrom those of the strain gauges R21 to R28. Because the strain gaugesare attached such that they have the maximum sensitivity in the line ofthe arrangement, the sensitivities of the strain gauges R11 to R18 andR31 to R38 are determined by the angles between the Y axis, along whichthe force Fy is applied, and the respective strain gauge groups.

The same can apply to an X-axial force Fx. Thus, an X- or Y-axial forcecan be calculated by Equation 5.

Next, FIG. 18 shows a state of displacement of the diaphragm 5 when aZ-axial force Fz is applied. FIG. 19 shows changes in the strain gaugesR11 to R38. In the bridge circuits shown in FIG. 16, V1, V2, and V3 donot change because their changes in resistance value cancel each other.V4, V5, and V6 change in accordance with the Z-axial force Fz.Therefore, the force Fz can be obtained by Equation 6.Fz=V4+V5+V6  [Equation 6]

Next, when a moment Mx is applied to the second member 3, a force torotate around the X axis is applied. As a result, Z-axial forces Fz areapplied to the diaphragms 4 to 6. In FIG. 20, suppose that the moment Mxis applied so that the diaphragms 4 and 6 are pushed from the front sidetoward the back side of FIG. 20, and the diaphragm 5 is pulled from theback side toward the front side of FIG. 20. When the distance from theorigin O to the center of each of the diaphragms 4 to 6 is R, thedistance from the center of each of the diaphragms 4 and 6 to the X axisis R/2, and the distance from the center of the diaphragm 5 to the Xaxis is R. Therefore, the moment Mx around the X axis is expressed byEquation 7.Mx=(V4·R/2)−(V5·R)+(V6·R/2)  [Equation 7]

Next, when a moment My is applied to the second member 3, the moment Myaround the Y axis is expressed by Equation 8 because the distance fromthe center of each of the diaphragms 4 and 6 to the Y axis is root 3R/2.$\begin{matrix}\begin{matrix}{{My} = {\left( {V\quad{4 \cdot \left. \sqrt{}3 \right.}{R/2}} \right) + {V\quad{5 \cdot 0}} - \left( {V\quad{6 \cdot \left. \sqrt{}3 \right.}{R/2}} \right)}} \\{= {\left. \sqrt{}3 \right.{R/2}\left( {{V\quad 4} - {V\quad 6}} \right)}}\end{matrix} & \left\lbrack {{Equation}\quad 8} \right\rbrack\end{matrix}$

Next, FIG. 21 shows a state of displacement of diaphragms 4 to 6 when aclockwise moment Mz around the Z axis is applied. FIG. 22 shows changesin the strain gauges R11 to R38. Strains are generated on the straingauge groups R15 to R18, R21 to R24, and R35 to R38 in directions thatbring about the maximum sensitivities, and V1, V2, and V3 of FIG. 16change with the highest sensitivities.

On the other hand, because the strain gauge groups R11 to R14, R25 toR28, and R31 to R34 are arranged on the lines that bring about theminimum sensitivities of the strain gauges, V4, V5, and V6 of FIG. 16scarcely change. Therefore, the moment Mz is expressed by Equation 9.Mz=V1+V2+V3  [Equation 9]

By calculating using Equations 5 to 9 as described above, the forces andmoments can be obtained. For example, the calculation may be made with amicro controller or a computer after the output voltages V1 to V6 areA/D-converted.

When the output voltages corresponding to forces Fx, Fy, and Fz andmoments Mx, My, and Mz to the multiaxial sensor 1 are Vfx, Vfy, Vfz,Vmx, Vmy, and Vmz, and the loads actually applied to the multiaxialsensor 1 are Fx, Fy, Fz, Mx, My, and Mz, they are in the relation ofEquation 10. $\begin{matrix}{\begin{bmatrix}{Vfx} \\{Vfy} \\{Vfz} \\{Vmx} \\{Vmy} \\{Vmz}\end{bmatrix} = {{{\lbrack A\rbrack\quad\begin{bmatrix}{Fx} \\{Fy} \\{Fz} \\{Mx} \\{My} \\{Mz}\end{bmatrix}}\quad\lbrack A\rbrack}:{{Calibration}\quad{matrix}}}} & \left\lbrack {{Equation}\quad 10} \right\rbrack\end{matrix}$

When both sides of the equation are multiplied by [A]−1 from the left,Equation 11 is obtained. $\begin{matrix}{\quad{\begin{bmatrix}{Fx} \\{Fy} \\{Fz} \\{Mx} \\{My} \\{Mz}\end{bmatrix} = {\lbrack A\rbrack^{- 1}\begin{bmatrix}{Vfx} \\{Vfy} \\{Vfz} \\{Vmx} \\{Vmy} \\{Vmz}\end{bmatrix}}}} & \left\lbrack {{Equation}\quad 11} \right\rbrack\end{matrix}$

Thereby, accurate 6-axial forces and moments can be obtained from theoutput voltages.

Next, a sixth embodiment of the present invention will be described withreference to FIGS. 23 and 24. FIG. 23 is a central vertical sectionalfront view of a multiaxial sensor 1 according to the sixth embodiment.FIG. 24 is a plan view showing the arrangement of strain gauges R11 toR48 when the multiaxial sensor 1 is transparently viewed in the reversedirection to the Z-axial direction. In the sixth embodiment, themultiaxial sensor 1 is made into one disk shape as a whole, and has fourdiaphragms 4 to 7. This multiaxial sensor 1 is a 6-axis sensor formeasuring accelerations along perpendicular three axes inthree-dimensional space, and angular accelerations around the respectiveaxes. A portion of the multiaxial sensor 1 other than the diaphragms 4to 7, for example, the outer peripheral portion, is fixed to an object15 to be measured.

The diaphragms 4 to 7 are arranged like those of the first embodiment.However, differently from the first embodiment, no diaphragms 4 to 7 areopposed. Operative bodies 16, 17, 18, and 19 to be displaced whenreceiving accelerations are provided at the centers of the respectivediaphragms 4 to 7. One end of each of the operative bodies 16 to 19 isfixed to the corresponding one of the diaphragms 4 to 7, and the otherend is free. The operative bodies 16 to 19 have the same shape.

Each of the strain gauges R11 to R48 may be a metallic foil strain gaugelike the first embodiment, or a piezoresistance element like the secondembodiment. The other construction is the same as that of the firstembodiment, and thus the description thereof is omitted.

In this embodiment, the origin O is defined at the center of a segmentextending between the gravity point G of the operative body 16 and thegravity point G of the operative body 18; the X axis is defined toextend horizontally rightward; the Y axis is defined to extend frontwardperpendicularly to FIG. 23; and the Z axis is defined to extendvertically downward.

A principle for detecting an acceleration or angular acceleration foreach axis according to this embodiment will be described.

When receiving an X-axial acceleration, the operative bodies 16 to 19are displaced as shown in FIG. 25 and strains are generated in thediaphragms 4 to 7. At this time, in the strain gauges R11 to R48, thereare changes in the strain gauges that are X-axially disposed, as shownin FIG. 26.

A case wherein a Y-axial acceleration ay is received is different fromthe case wherein the X-axial acceleration ax is received, only in thefeature of being shifted by 90 degrees, and thus the description thereofis omitted.

Next, when a Z-axial acceleration az is received, the operative bodies16 to 19 are displaced as shown in FIG. 27. Thereby, the strain gaugesR11 to R48 changes as shown in FIG. 28.

Next, cases wherein angular accelerations around the respective axes areapplied will be described. Suppose that accelerations applied to theoperative bodies 16 to 19 perpendicularly to the diaphragms 4 to 7 areaz1, az2, az3, and az4. When an angular acceleration alpha y around theY axis is applied, the accelerations az1 and az3 are applied to theoperative bodies 16 and 18, and thereby the operative bodies 16 and 18are displaced and strains are generated in the diaphragms 4 to 7. FIG.30 shows changes in the strain gauges R11 to R48 at this time.

Next, when an angular acceleration alpha z around the Z axis is applied,the operative bodies 16 to 19 are displaced in the same rotationdirection around the Z axis, and strains are generated in the diaphragms4 to 7. FIG. 31 shows changes in the strain gauges R11 to R48 at thistime.

Table 2 shows changes in the resistance values of the strain gauges R11to R48 to the above-described accelerations and angular accelerations.

[Table 2] TABLE 2 Force R11 R12 R13 R14 R15 R16 R17 R18 R21 R22 R23 R24R25 R26 R27 R28 ax − + − + − + − + ay − + − + − + − + az + − − + + −− + + − − + + − − + αx − + + − − + + − αy − + + − − + + − αz − + − + − +− + Force R31 R32 R33 R34 R35 R36 R37 R38 R41 R42 R43 R44 R45 R46 R47R48 ax − + − + − + − + ay − + − + − + − + az + − − + + − − + + − − + + −− + αx + − − + + − − + αy + − − + + − − + αz + − + − + − + −

Although this multiaxial sensor 1 is an aggregate of four 3-axisacceleration sensors, an angular acceleration can be detected from anacceleration by using the following principle. First, in circularmovement, i.e., rotational movement, on the circumference of a circlehaving its radius r, the tangential acceleration a is a=r multiplied byalpha, that is, alpha=a/r where alpha is the angular acceleration.

When viewed from the center of the multiaxial sensor 1, the tangentialacceleration a is the same as the acceleration applied to each of theoperative bodies 16 to 19. Because the radius r is fixed, after all,angular accelerations can be obtained if X-, Y-, and Z-axialaccelerations are obtained.

Using that, accelerations and angular accelerations can be detected bythe calculation of Equation 12.ax=(R22+R42)−(R23+R43)ay=(R16+R36)−(R17+R37)az=(R11+R28+R34+R45)−(R13+R26+R32+R47)αx=(R25+R46)−(R27+R48)αy=(R14+R33)−(R12+R31)αz=(R18+R24+R35+R41)−(R15+R21+R38+R44)  [Equation 12]

On the other hand, the accelerations and angular accelerations can bedetected also by bridge circuits constructed as shown in FIG. 32, towhich a constant voltage or a constant current is applied.

In this embodiment, the sensor sensitivity can be controlled bycontrolling the dimensions, such as the thickness of each of thediaphragms 4 to 7, the thickness and width of each beam, and the size ofeach of the operative bodies 16 to 19. Although an angular accelerationis obtained in this embodiment, the angular acceleration may beintegrated to obtain an angular velocity.

Next, a seventh embodiment of the present invention will be describedwith reference to FIG. 33. In the seventh embodiment, although thestructure of the multiaxial sensor 1 is the same as that of the sixthembodiment, the construction of each bridge is modified. As shown inFIG. 33, each bridge is constituted by four strain gauges linearlydisposed on each of the diaphragms 4 to 7.

Vx1 and Vx2 are voltage signals indicating an X-axial acceleration, andVy1 and Vy2 are voltage signals indicating a Y-axial acceleration. Vz1to Vz4 are voltage signals indicating a Z-axial acceleration. Bycarrying out the calculation shown by Equation 13 on the basis of thosesignals, accelerations and angular accelerations can be sensitivelydetected. $\begin{matrix}{{{ax} = {\left( {{Vx}\quad 2} \right) - \left( {{Vx}\quad 1} \right)}}{{ay} = {\left( {{Vy}\quad 2} \right) - \left( {{Vy}\quad 1} \right)}}{{az} = {\left( {{Vz}\quad 1} \right) + \left( {{Vz}\quad 2} \right) + \left( {{Vz}\quad 3} \right) + \left( {{Vz}\quad 4} \right)}}{{\alpha\quad x} = {\left( {{Vz}\quad 2} \right) - \left( {{Vz}\quad 4} \right)}}{{\alpha\quad y} = {\left( {{Vz}\quad 1} \right) - \left( {{Vz}\quad 3} \right)}}{{\alpha\quad z} = {\left( {{Vx}\quad 1} \right) + \left( {{Vx}\quad 2} \right) + \left( {{Vy}\quad 1} \right) + \left( {{Vy}\quad 2} \right)}}\begin{matrix}\quad & \overset{{Vx}\quad 2}{\rightarrow} & \quad \\{{Vy}\quad\left. 2\uparrow \right.} & \quad & {\left. \downarrow{Vy} \right.\quad 1} \\\quad & \underset{{Vx}\quad 1}{\leftarrow} & \quad\end{matrix}} & \left\lbrack {{Equation}\quad 13} \right\rbrack\end{matrix}$

Accelerations ax and ay can be detected by using either Vx1 and Vx2 orVy1 and Vy2. In any case, the sensitivity can be improved bydifferential.

Next, an eighth embodiment of the present invention will be describedwith reference to FIGS. 34 and 35. FIG. 34 is a plan view of amultiaxial sensor 1 of the eighth embodiment. FIG. 35 is a centralvertical sectional front view of the multiaxial sensor 1. Thismultiaxial sensor 1 is a 6-axis sensor for measuring accelerations alongperpendicular three axes in three-dimensional space, and angularaccelerations around the respective axes, like the sixth embodiment. Inthis multiaxial sensor 1, piezoresistance elements 10 are formed on asilicon substrate 20 by using a semiconductor process, and bridgecircuits for detecting accelerations and angular accelerations areconstructed using the piezoresistance elements 10. Further, a glasssubstrate is bonded to a silicon wafer 11, and a pedestal 21 andoperative bodies 16 to 19 are formed by using a micro machiningtechnique. Although the gauge factor varies from plain orientation toplain orientation of the silicon wafer 11 on which the piezoresistanceelement 10 is formed, unevenness in sensitivity can be suppressed to theminimum by selecting a proper plain orientation.

In this embodiment, the piezoresistance elements 10, each of which is adetector, serve as beams 22 for connecting the operative bodies 16 to 19and the pedestal 21. In addition, by providing openings 23, theoperative bodies 16 to 19 become easy to be displaced when receivingaccelerations, and thereby the sensitivity is improved. Each opening 23may be rectangular or circular, or may not always be provided.

According to this embodiment, a processing circuit for sensor signals,and so on, can be simultaneously formed on the silicon substrate 20 byusing a semiconductor process, and thus the signal processing circuitand the sensor can be integrated into a compact form. As a result, wiresbetween the signal processing circuit and the detectors of the sensorcan be shortened. This makes the sensor hard to be influenced by noiseand enables a stable operation. In addition, because the multiaxialsensor 1 can be reduced in size, it is advantageous also in view of anarea for setting. Further, by using such a semiconductor process and amicro machining technique, the sensor can be efficiently manufactured ata low cost, and the accuracy in assembling can be improved.

Next, a ninth embodiment of the present invention will be described withreference to FIGS. 36 and 37. FIG. 36 is a central vertical sectionalfront view of a multiaxial sensor 1 according to the ninth embodiment ofthe present invention. FIG. 37 is a plan view showing the arrangement ofstrain gauges when the multiaxial sensor 1 is Z-axially transparentlyviewed from the position of the second member 3. The multiaxial sensor 1of this embodiment is a 6-axis force sensor for measuring forces ofperpendicular three axes in three-dimensional space, and moments aroundthe respective axes, like the multiaxial sensor 1 of the firstembodiment. The multiaxial sensor 1 of this embodiment differs inconstruction from the multiaxial sensor 1 of the first embodiment mainlyin the point that each of the first and second members 2 and 3 of thisembodiment has only one diaphragm 4 while each of the first and secondmembers 2 and 3 of the first embodiment has four diaphragms 4, 5, 6, and7.

The multiaxial sensor 1 of this embodiment includes a first member 2, asecond member 3, and operative bodies 16 to 19. The first and secondmembers 2 and 3 are disposed so that the upper face of the first member2 is opposed to the lower face of the second member 3. The first andsecond members 2 and 3 are connected by the operative bodies 16 to 19.

The diaphragms 4 provided in the respective first and second members 2and 3 are formed into circular shapes having their radii equal to eachother. An annular thick portion 24 is formed near the edge of eachdiaphragm. Four columnar operative bodies 16 to 19 are formed on theupper surface of the diaphragm 4 of the first member 2. The operativebody 16 is formed in the X-axial positive direction; the operative body17 is formed in the Y-axial negative direction; the operative body 18 isformed in the X-axial negative direction; and the operative body 19 isformed in the Y-axial positive direction. They are formed at the samedistance from the origin O. The upper ends of the operative bodies 16 to19 are bonded by welding to the lower surface of the diaphragm 4 of thesecond member 3 opposed to the first member 2.

The first member 2 and the operative bodies 16 to 19 may be formed byseparate members, or the first and second members 2 and 3 and theoperative bodies 16 to 19 may be formed from one body by cutting. Thesecond member and the operative bodies 16 to 19 may be connected withbolts.

As shown in FIG. 37, twenty strain gauges R11 to R45 are disposed on thelower surface of the diaphragm 4 of the first member 2. The straingauges R11 to R14 are disposed on the lower surface of the diaphragm 4of the second member 2 at positions corresponding to the edge of theoperative body 16. The strain gauges R11 and R12 are disposed on the Xaxis such that the strain gauge R12 is nearer to the origin O than thestrain gauge R11. The strain gauges R13 and R14 are disposed on an axisperpendicular to the X axis and the central axis of the operative body16 such that the strain gauge R13 corresponds to the Y-axial positivedirection and the strain gauge R14 corresponds to the Y-axial negativedirection. The strain gauge R15 is disposed on the edge of the diaphragm4 at a position corresponding to the X-axial positive direction.

Likewise, on the lower surface of the diaphragm 4 of the second member2, the strain gauges R21 to R24 are disposed at positions correspondingto the edge of the operative body 17; the strain gauges R31 to R34 aredisposed at positions corresponding to the edge of the operative body18; and the strain gauges R41 to R44 are disposed at positionscorresponding to the edge of the operative body 19. Further, on the edgeof the diaphragm 4, the strain gauge R25 is disposed at a positioncorresponding to the Y-axial negative direction; the strain gauge R35 isdisposed at a position corresponding to the X-axial negative direction;and the strain gauge R45 is disposed at a position corresponding to theY-axial positive direction.

The arrangement positions of the strain gauges R15, R25, R35, and R45are not limited to the above. They can be disposed at any positionscorresponding to the edge of the diaphragm 4 or the edges of theoperative bodies 16 to 19 on the lower surface of the diaphragm 4 of thefirst member 2 as far as they are arranged around the origin O atangular intervals of 90 degrees and at the same distance from the originO.

Next, a principle for detecting a force or moment for each componentwill be described. In the below description, it is assumed that thefirst member 2 is fixed and the force or moment is applied to the secondmember 3.

FIG. 38 shows a state of the multiaxial sensor 1 when an X-axial forceFx is applied to the second member 3. In this state, the diaphragms 4 ofthe first and second members 2 and 3 have been displaced as shown inFIG. 38, and strains are detected. FIG. 39 shows changes in theresistance values of the strain gauges R11 to R45 at this time. Thedescription of a case wherein a Y-axial force Fy is applied to thesecond member 3 is omitted here because it can be understood by siftingby 90 degrees the state when the X-axial force Fx is applied. FIG. 40shows a state of the multiaxial sensor 1 when a Z-axial force Fz isapplied to the second member 3. FIG. 41 shows changes in the resistancevalues of the strain gauges R11 to R45 when the Z-axial force Fz isapplied to the second member 3.

FIG. 42 shows a state of the multiaxial sensor 1 when an X-axial momentMx is applied to the second member 3. FIG. 43 shows changes in theresistance values of the strain gauges R11 to R45 at this time. Thedescription of a case wherein a Y-axial moment My is applied to thesecond member 3 is omitted here because it can be understood by siftingby 90 degrees the state when the X-axial moment Mx is applied. When aZ-axial moment Mz is applied to the second member 3, the second member 3is rotated around the Z axis. FIG. 44 shows changes in the resistancevalues of the strain gauges R11 to R45 when the Z-axial moment Mz isapplied to the second member 3.

Table 3 shows changes in the strain gauges R11 to R45 to theabove-described forces and moments.

[Table 3] TABLE 3 Force R11 R12 R13 R14 R15 R21 R22 R23 R24 R25 Fx + −− + − Fy + − + − + Fz + − + − Mx − − + My + + − Mz − + − + Force R31 R32R33 R34 R35 R41 R42 R43 R44 R45 Fx + − + + − Fy + − + − − Fz + − + −Mx + + − My − − + Mz + − + −

Using the above nature, the forces and moments can be detected by thecalculation of Equation 14. As a matter of course, the calculationmethod is not limited to Equation 14.Fx=R41−R22Fy=R13−R34Fz=R15+R25+R35+R45Mx=(R43+R44)−(R23+R24)My=(R11+R12)−(R31+R32)Mz=(R14+R33)−(R21+R42)  [Equation 14]

The above calculation can be efficiently carried out if bridge circuitsare constructed as shown in FIG. 45 and a constant voltage or a constantcurrent is applied to them to detect forces and moments. FIG. 45 shows acase wherein a constant voltage is applied. In this embodiment, as shownin FIG. 45, the circuits for detecting Fx and Fy are half bridges thatcan not compensate errors of output values due to a change intemperature. Therefore, a dummy circuit as shown in FIG. 46 is furtherprovided, and the difference from the output voltage V1 of the dummycircuit is calculated. Thereby, drifts or common mode noises due to achange in the surrounding temperature cancel each other, and thus anoutput can be stably obtained. Strain gauges Rd1 and Rd2 in FIG. 46 aredisposed at positions where strains are scarcely generated when a loadis applied to the multiaxial sensor 1, such as a fixed portion 8.

Either of resistances Ra and Rb included in the bridge circuit fordetecting Fz is a dummy fixed resistance on circuit. The values of theresistances Ra and Rb are preferably Ra=(R15+R25) and Rb=(R35+R45).

As described above, in the multiaxial sensor 1 of this embodiment, onediaphragm 4 is provided for each of the first and second members 2 and3. Therefore, in comparison with a case wherein a plurality ofdiaphragms are provided for each of the first and second members 2 and3, the multiaxial sensor 1 can be reduced in size. In addition, becausethe shape of the multiaxial sensor is simple, the cost required forcutting can be reduced.

Further, in the multiaxial sensor 1 of this embodiment, in comparisonwith a case wherein a plurality of diaphragms are provided for each ofthe first and second members 2 and 3, multiaxial forces and moments canbe measured with less strain gauges. Therefore, the cost for the straingauges and the cost for wiring can be reduced.

Next, a tenth embodiment of the present invention will be described withreference to FIG. 47. FIG. 47 is a plan view showing the arrangement ofstrain gauges R11 to R35 when a multiaxial sensor 1 according to thetenth embodiment is Z-axially transparently viewed from the position ofthe second member 3. The multiaxial sensor 1 of this embodiment is a6-axis force sensor for measuring forces of perpendicular three axes inthree-dimensional space, and moments around the respective axes, likethe multiaxial sensor 1 of the first embodiment. The multiaxial sensor 1of this embodiment differs in construction from the multiaxial sensor 1of the first embodiment mainly in the point that each of the first andsecond members 2 and 3 of this embodiment has only one diaphragm 4 whileeach of the first and second members 2 and 3 of the first embodiment hasfour diaphragms 4, 5, 6, and 7.

The multiaxial sensor 1 of this embodiment includes a first member 2, asecond member 3, and operative bodies 16 to 18. The first and secondmembers 2 and 3 are disposed so that the upper face of the first member2 is opposed to the lower face of the second member 3. The first andsecond members 2 and 3 are connected by the operative bodies 16 to 18.

The diaphragms 4 provided in the respective first and second members 2and 3 are formed into circular shapes having their radii equal to eachother. An annular thick portion 24 is formed near the edge of eachdiaphragm. Three columnar operative bodies 16 to 18 are formed on theupper surface of the diaphragm 4 of the first member 2. The operativebody 16 is formed on a segment CO extending from the origin O so as toform an angle of 120 degrees from the Y-axial negative direction to theX-axial positive direction; the operative body 17 is formed on the Yaxis in the negative direction; and the operative body 18 is formed on asegment DO extending from the origin O so as to form an angle of 120degrees from the Y-axial negative direction to the X-axial negativedirection. They are formed at the same distance from the origin O. Theupper ends of the operative bodies 16 to 18 are bonded by welding to thelower surface of the diaphragm 4 of the second member 3 opposed to thefirst member 2.

As shown in FIG. 47, fifteen strain gauges R11 to R35 are disposed onthe lower surface of the diaphragm 4 of the first member 2. On the lowersurface of the diaphragm 4 of the second member 2, the strain gauges R11to R14 are disposed at positions corresponding to the edge of theoperative body 16; the strain gauges R21 to R24 are disposed atpositions corresponding to the edge of the operative body 17; the straingauges R31 to R34 are disposed at positions corresponding to the edge ofthe operative body 18; and the strain gauges R15, R25, and R35 aredisposed on the edge of the diaphragm 4.

A principle for detecting a force or moment for each axis will bedescribed. A strain gauge group constituted by a plurality of straingauges arranged on a straight line becomes the highest in rate of thechange in resistance value and increases in sensitivity to a strain whenthe tensile or compressive strain is applied along the line of thearrangement. Six strain gauge groups of this embodiment, constituted bythe strain gauges R11 and R12, the strain gauges R13 and R14, the straingauges R21 and R22, the strain gauges R23 and R24, the strain gauges R31and R32, and the strain gauges R33 and R34, differ from one another indirection in which the sensitivity increases. However, when thesensitivity of each strain gauge group is considered by resolving intoX-, Y-, and Z-axial vectors, a force or moment having 6-axial componentscan be detected.

Bridge circuits as shown in FIG. 48 are constructed for the straingauges R11 to R33 shown in FIG. 47, and a constant voltage or a constantcurrent is applied to them. In this embodiment, any of resistances Ra toRo included in the bridge circuits of FIG. 48 is a dummy fixedresistance on circuit. The values of the resistances Ra to Ro arepreferably substantially equal to the respective strain gauges R11 toR33.

By the full bridge circuits of FIG. 48, the strain gauges R11 and R12can detect as a voltage Va a force component at 30 degrees from theX-axial positive direction to the Y-axial positive direction; the straingauges R13 and R14 can detect as a voltage Vb a force component at 60degrees from the X-axial positive direction to the Y-axial negativedirection; the strain gauges R21 and R22 can detect as a voltage Vc aforce component at 180 degrees from the X-axial positive direction tothe Y-axial positive direction; the strain gauges R23 and R24 can detectas a voltage Vd a force component at 90 degrees from the X-axialpositive direction to the Y-axial negative direction; the strain gaugesR31 and R32 can detect as a voltage Ve a force component at 150 degreesfrom the X-axial positive direction to the Y-axial positive direction;and the strain gauges R33 and R34 can detect as a voltage Vf a forcecomponent at 120 degrees from the X-axial positive direction to theY-axial negative direction. On the other hand, by the half bridgecircuits of FIG. 48, the strain gauge R15 can detect as a voltage Vz1 aZ-axial force component at the center of the operative body 16; thestrain gauge R25 can detect as a voltage Vz2 a Z-axial force componentat the center of the operative body 17; and the strain gauge R35 candetect as a voltage Vz1 a Z-axial force component at the center of theoperative body 18.

When the output voltages Va to Vf from the full bridge circuits areresolved into X- and Y-axial vectors, they can be expressed by Equation15.Va=(Vax,Vax)=(Va/2,Va·√{square root over ( )}3/2)Vb=(Vbx,Vby)=(Vb·√{square root over ( )}3/2,−Vb/2)Vc=(Vcx,Vcy)=(Vc,0)Vd=(Vdx,Vdy)=(0,Vd)Ve=(Vex,Vey)=(Ve/2,−Ve·√{square root over ( )}3/2)Vf=(Vfx,Vfy)=(Vf·√{square root over ( )}3/2,Vf/2)  [Equation 15]

Therefore, when the X-axial resultant force applied to the second member3 is Fx and the Y-axial resultant force is Fy, they can be detected asin Equation 16. $\begin{matrix}{\begin{matrix}{{Fx} = {{Vax} + {Vbx} + {Vcx} + {Vdx} + {Vex} + {Vfx}}} \\{= {\left( {{Va}/2} \right) + \left( {{Vb} \cdot {\left. \sqrt{}3 \right./2}} \right) + {Vc} + \left( {{Ve}/2} \right) + \left( {{Vf} \cdot {\left. \sqrt{}3 \right./2}} \right)}}\end{matrix}\begin{matrix}{{Fy} = {{Vay} + {Vby} + {Vcy} + {Vdy} + {Vey} + {Vfy}}} \\{= {\left( {{Va} \cdot {\left. \sqrt{}3 \right./2}} \right) - \left( {{Vb}/2} \right) + {Vd} - \left( {{Ve} \cdot {\left. \sqrt{}3 \right./2}} \right) + \left( {{Vf}/2} \right)}}\end{matrix}} & \left\lbrack {{Equation}\quad 16} \right\rbrack\end{matrix}$

On the other hand, the output voltages Vz1, Vz2, and Vz3 of the halfbridge circuits change in accordance with the Z-axial force Fz.Therefore, the force fz can be obtained by Equation 17.Fz=Vz1+Vz2+Vz3  [Equation 17]

Next, when a moment Mx is applied to the second member 3, a force torotate around the X axis is applied. In this example, it is supposedthat the moment Mx acts so as to push a Y-axial positive portion fromthe Z-axial negative direction to the Z-axial positive direction, andpull a Y-axial negative portion from the Z-axial positive direction tothe Z-axial negative direction. When the distance from the origin O tothe center of each of the operative bodies 16 to 18 is R, the distancefrom the center of each of the operative bodies 16 and 18 to the X axisis R/2, and the distance from the center of the operative body 17 to theX axis is R. Therefore, in consideration of the direction of the forceacting on the center of each of the operative bodies 16 to 18, themoment Mx around the X axis is expressed by Equation 18.Mx=(Fz1·R/2)−(Fz2·R)+(Fz3·R/2)  [Equation 18]

Next, a case will be described wherein a moment My is applied to thesecond member 3 so as to push an X-axial positive portion from theZ-axial positive direction to the Z-axial negative direction, and pullan X-axial negative portion from the Z-axial negative direction to theZ-axial positive direction. In this embodiment, the distance from thecenter of each of the operative bodies 16 and 18 to the Y axis is root3R/2, and the center of the operative body 17 is on the Y axis.Therefore, in consideration of the direction of the force acting on thecenter of each of the operative bodies 16 to 18, the moment My aroundthe Y axis is expressed by Equation 19. $\begin{matrix}\begin{matrix}{{My} = {\left( {{Fz}\quad{1 \cdot \left. \sqrt{}3 \right.}{R/2}} \right) + {{Fz}\quad{2 \cdot 0}} - \left( {{Fz}\quad{3 \cdot \left. \sqrt{}3 \right.}{R/2}} \right)}} \\{= {{\left. \sqrt{}3 \right./2}\left( {{{Fz}\quad 1} - {{Fz}\quad 3}} \right)}}\end{matrix} & \left\lbrack {{Equation}\quad 19} \right\rbrack\end{matrix}$

Next, a case will be described wherein a clockwise moment Mz around theZ axis is applied to the second member 3. In this case, strains aregenerated on three strain gauge groups constituted by the strain gaugesR13 and R14; R21 and R22; and R33 and R34, in directions that bringabout the maximum sensitivities. Thus, the output voltages Vb, Vc, andVf of the circuits of FIG. 48 change with the highest sensitivities. Onthe other hand, three strain gauge groups constituted by the straingauges R11 and R12; R23 and R24; and R31 and R32 are arranged on thelines that bring about the minimum sensitivities of the strain gauges.Thus, the output voltages Va, Vd, and Ve of the circuits of FIG. 48scarcely change. Therefore, in consideration of the direction of theforce acting on the center of each of the operative bodies 16 to 18, themoment Mz is expressed by Equation 20.Mz=−Vb+Vc−Vf  [Equation 20]

By calculating using Equations 15 to 20 as described above, the forcesand moments can be obtained. For example, the calculation may be madewith a micro controller or a computer after the output voltages Va to Vfand Vz1 to Vz3 are A/D-converted.

As described above, in the multiaxial sensor 1 of this embodiment, asimilar effect to that of the ninth embodiment can be obtained. Inaddition, because multiaxial forces and moments can be calculated byforming three operative bodies on the diaphragm, the construction of themultiaxial sensor 1 can be further simplified.

Although the preferred embodiments of the present invention have beendescribed as above, the present invention is never limited to theabove-described embodiments, and various changes in design can be madewithin the description of the claims. For example, in theabove-described first to tenth embodiments, the strain gauges areindividually attached to the first member 2. However, the presentinvention is not limited to that. Utilizing the feature that all thestrain gauges are attached on one plane, strain gauges may be integratedon one base plate for each of the diaphragms 4 to 7 to be attached tothe diaphragms 4 to 7. Otherwise, all the strain gauges may beintegrated on one base plate to be attached. Conductive wiring forconstructing each gauge or circuit may be made of a thin film ofchromium oxide formed by sputtering or deposition on a thin insulatingfilm formed on each of the diaphragms 4 to 7 by sputtering ordeposition. Because a strain gauge thus constructed is ten times or morehigher in gauge factor than a general foil strain gauge, the sensitivitycan be improved ten times or more in comparison with a case wherein sucha general foil strain gauge is used. In addition, the work process forattaching the strain gauges to the diaphragms 4 to 7 is simplified; thework efficiency is improved; the productivity is remarkably improved;and a reduction of cost can be intended.

In the above-described first to tenth embodiments, the multiaxialsensors for detecting 6-axis forces and moments or accelerations andangular accelerations have been described. However, the presentinvention is not limited to those. For example, a multiaxial sensor maybe used as a 2-axis sensor for detecting only forces along two axes of Xand Y axes.

In the above-described first to tenth embodiments, the diaphragms arearranged at regular angular intervals. However, the present invention isnot limited to that. Further, the diaphragms may not always be arrangedat the same distance from the origin O.

In the above-described ninth and tenth embodiments. the operative bodiesare arranged at regular angular intervals. However, the presentinvention is not limited to that. Further, the operative bodies may notalways be arranged at the same distance from the origin O.

INDUSTRIAL APPLICABILITY

The present invention is optimum as a multiaxial sensor capable ofmeasuring the direction and magnitude of at least one of six componentsof externally applied forces along perpendicular three axes, andexternally applied moments around the respective axes. Therefore, forexample, in a humanoid robot expected to be put in practice in the fieldof amusement, if a multiaxial sensor of the present invention is set ina hand or leg of the humanoid robot, forces and moments applied to thehand or leg of the humanoid robot can be detected in high responsibilityand high accuracy at a cost lower than a conventional sensor.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1A]

A view showing a multiaxial sensor according to a first embodiment ofthe present invention, which is a plan view showing the arrangement ofstrain gauges when Z-axially transparently viewed from the position of asecond member.

[FIG. 1B]

A view showing the multiaxial sensor according to the first embodimentof the present invention, which is a central vertical sectional frontview.

[FIG. 2]

A perspective representation showing Cartesian coordinate axes.

[FIG. 3]

A central vertical sectional front view showing displacement when aforce Fx is applied to the multiaxial sensor.

[FIG. 4]

A plan view showing changes in the resistance values of the straingauges when the force Fx is applied to the multiaxial sensor.

[FIG. 5]

A central vertical sectional front view showing displacement when aforce Fz is applied to the multiaxial sensor.

[FIG. 6]

A plan view showing changes in the resistance values of the straingauges when the force Fz is applied to the multiaxial sensor.

[FIG. 7]

A central vertical sectional front view showing displacement when amoment Mx is applied to the multiaxial sensor.

[FIG. 8]

A plan view showing changes in the resistance values of the straingauges when the moment Mx is applied to the multiaxial sensor.

[FIG. 9]

A plan view showing changes in the resistance values of the straingauges when a moment Mz is applied to the multiaxial sensor.

[FIG. 10]

Circuit diagrams showing examples of bridge circuits for the multiaxialsensor.

[FIG. 11]

A central vertical sectional front view showing a multiaxial sensoraccording to a second embodiment.

[FIG. 12]

Circuit diagrams showing examples of bridge circuits according to athird embodiment.

[FIG. 13]

A central vertical sectional front view showing a multiaxial sensoraccording to a fourth embodiment.

[FIG. 14]

A block diagram showing amplifier circuits and a judgment procedure ofthe multiaxial sensor according to a fourth embodiment.

[FIG. 15]

A plan view showing the arrangement of strain gauges when a multiaxialsensor according to a fifth embodiment is Z-axially transparently viewedfrom the position of a second member.

[FIG. 16]

Circuit diagrams showing examples of bridge circuits for the multiaxialsensor.

[FIG. 17]

A central vertical sectional front view showing displacement when aforce Fy is applied to the multiaxial sensor.

[FIG. 18]

A central vertical sectional front view showing displacement when aforce Fz is applied to the multiaxial sensor.

[FIG. 19]

A plan view showing changes in the resistance values of the straingauges when the force Fz is applied to the multiaxial sensor.

[FIG. 20]

A central vertical sectional front view showing displacement when amoment Mx is applied to the multiaxial sensor.

[FIG. 21]

A central vertical sectional front view showing displacement when amoment Mz is applied to the multiaxial sensor.

[FIG. 22]

A plan view showing changes in the resistance values of the straingauges when the moment Mz is applied to the multiaxial sensor.

[FIG. 23]

A central vertical sectional front view showing a multiaxial sensoraccording to a sixth embodiment.

[FIG. 24]

A plan view showing the arrangement of strain gauges when the multiaxialsensor according to the sixth embodiment is transparently viewed in thereverse direction of the Z axis.

[FIG. 25]

A central vertical sectional front view showing displacement when anacceleration ax is applied to the multiaxial sensor.

[FIG. 26]

A plan view showing changes in the resistance values of the straingauges when the acceleration ax is applied to the multiaxial sensor.

[FIG. 27]

A central vertical sectional front view showing displacement when anacceleration az is applied to the multiaxial sensor.

[FIG. 28]

A plan view showing changes in the resistance values of the straingauges when the acceleration ax is applied to the multiaxial sensor.

[FIG. 29]

A central vertical sectional front view showing displacement when anangular acceleration alpha y is applied to the multiaxial sensor.

[FIG. 30]

A plan view showing changes in the resistance values of the straingauges when the angular acceleration alpha y is applied to themultiaxial sensor.

[FIG. 31]

A plan view showing changes in the resistance values of the straingauges when an angular acceleration alpha z is applied to the multiaxialsensor.

[FIG. 32]

Circuit diagrams showing examples of bridge circuits for the multiaxialsensor.

[FIG. 33]

Circuit diagrams showing examples of bridge circuits according to aseventh embodiment.

[FIG. 34]

A plan view showing a multiaxial sensor according to an eighthembodiment.

[FIG. 35]

A central vertical sectional front view showing the multiaxial sensoraccording to the eighth embodiment.

[FIG. 36]

A central vertical sectional front view showing a multiaxial sensoraccording to a ninth embodiment.

[FIG. 37]

A plan view showing the arrangement of strain gauges when a multiaxialsensor according to the ninth embodiment is Z-axially transparentlyviewed from the position of a second member.

[FIG. 38]

A central vertical sectional front view showing displacement when aforce Fx is applied to the multiaxial sensor.

[FIG. 39]

A plan view showing changes in the resistance values of the straingauges when the force Fx is applied to the multiaxial sensor.

[FIG. 40]

A central vertical sectional front view showing displacement when aforce Fz is applied to the multiaxial sensor.

[FIG. 41]

A plan view showing changes in the resistance values of the straingauges when the force Fz is applied to the multiaxial sensor.

[FIG. 42]

A central vertical sectional front view showing displacement when aforce Mx is applied to the multiaxial sensor.

[FIG. 43]

A plan view showing changes in the resistance values of the straingauges when the force Mx is applied to the multiaxial sensor.

[FIG. 44]

A plan view showing changes in the resistance values of the straingauges when a force Mz is applied to the multiaxial sensor.

[FIG. 45]

Circuit diagrams showing examples of bridge circuits for the multiaxialsensor.

[FIG. 46]

A circuit diagram showing an example of a dummy circuit.

[FIG. 47]

A plan view showing the arrangement of strain gauges when a multiaxialsensor according to a tenth embodiment is Z-axially transparently viewedfrom the position of a second member.

[FIG. 48]

Circuit diagrams showing examples of bridge circuits according to thetenth embodiment.

[FIG. 49]

A perspective view showing a prior art multiaxial sensor.

DESCRIPTION OF REFERENCE NUMERAL

-   -   1: multiaxial sensor    -   2: first member    -   3: second member    -   4, 5, 6, 7: diaphragm    -   8: central shaft    -   10: piezoresistance element    -   16, 17, 18, 19: operative body    -   R11 to R48, R111 to R148: strain gauge

1. A 6-axis sensor for measuring 6-axis forces and moments or 6-axisaccelerations and angular accelerations, externally applied,characterized by comprising: a plurality of strain gauges disposed onone plane.
 2. The 6-axis sensor according to claim 1, characterized byfurther comprising a first diaphragm to which the plurality of straingauges are attached.
 3. The 6-axis sensor according to claim 2,characterized in that first diaphragms are arranged around a centralpoint of the plane at regular angular intervals and at the same distancefrom the central point.
 4. The 6-axis sensor according to claim 3,characterized in that the angular interval is 90 degrees.
 5. The 6-axissensor according to claim 4, characterized in that the diaphragms aredisposed in positive and negative directions on X and Y axes with anorigin being defined at the central point.
 6. The 6-axis sensoraccording to claim 3, characterized in that the angular interval is 120degrees.
 7. The 6-axis sensor according to claim 2, characterized inthat a thin portion of each first diaphragm is annular and provided witheight strain gauges, and the strain gauges are disposed at outer andinner edge portions of the first diaphragm on a line extending between acentral point of the first diaphragm and the central point of the plane,and at outer and inner edge portions of the first diaphragm on a lineperpendicular to the former line at the central point of the firstdiaphragm.
 8. The 6-axis sensor according to claim 2, characterized inthat the 6-axis sensor further comprises an operative body provided on acentral portion of the first diaphragm, and 6-axis accelerations andangular accelerations applied to the 6-axis sensor are measured.
 9. The6-axis sensor according to claim 2, characterized in that the 6-axissensor further comprises: a first member comprising the first diaphragm;a second member comprising a second diaphragm opposed to the firstdiaphragm and provided with no strain gauges; and a connecting shaftconnecting the opposed first and second diaphragms, and 6-axis forcesand moments applied between the first and second members are measured.10. The 6-axis sensor according to claim 2, characterized in that the6-axis sensor further comprises: a first member comprising the firstdiaphragm; a second member comprising a second diaphragm opposed to thefirst diaphragm and provided with a plurality of strain gauges disposedon one plane, and a connecting shaft connecting the opposed first andsecond diaphragms; and 6-axis forces and moments applied between thefirst and second members are measured.
 11. The 6-axis sensor accordingto claim 10, characterized in that the strain gauges of the first memberand the strain gauges of the second member are disposed symmetricallywith respect to a barycentric point of the 6-axis sensor.
 12. The 6-axissensor according to claim 11, characterized in that either outputs ofthe strain gauges of the first member and the strain gauges of thesecond member are adopted if the other outputs are out of apredetermined range.
 13. The 6-axis sensor according to claim 2,characterized in that only one diaphragm is disposed on the plane. 14.The 6-axis sensor according to claim 13, characterized in that the6-axis sensor further comprises operative bodies being in contact withthe first diaphragms at positions arranged around the central point ofthe plane at regular angular intervals and at the same distance from thecentral point, and 6-axis accelerations and angular accelerationsapplied to the 6-axis sensor are measured.
 15. The 6-axis sensoraccording to claim 13, characterized in that the 6-axis sensor furthercomprises: a first member comprising the first diaphragm; a secondmember comprising only one second diaphragm provided with no straingauges; and operative bodies connecting the first and second diaphragms,the first and second members are disposed so that a central point of thefirst diaphragm of the first member is opposed to a central point of thesecond diaphragm of the second member, and the operative bodies connectsthe first and second diaphragms at positions arranged around the centralpoints of the first and second diaphragms at regular angular intervalsand at the same distance from the central points, and 6-axis forces andmoments applied between the first and second members are measured. 16.The 6-axis sensor according to claim 13, characterized in that the6-axis sensor further comprises: a first member comprising the firstdiaphragm; a second member comprising a second diaphragm provided with aplurality of strain gauges disposed on one plane; and operative bodiesconnecting the first and second diaphragms, the first and second membersare disposed so that a central point of the first diaphragm of the firstmember is opposed to a central point of the second diaphragm of thesecond member, and the operative bodies connects the first and seconddiaphragms at positions arranged around the central points of the firstand second diaphragms at regular angular intervals and at the samedistance from the central points, and 6-axis forces and moments appliedbetween the first and second members are measured.
 17. The 6-axis sensoraccording to claim 16, characterized in that the strain gauges of thefirst member and the strain gauges of the second member are disposedsymmetrically with respect to a barycentric point of the 6-axis sensor.18. The 6-axis sensor according to claim 17, characterized in thateither outputs of the strain gauges of the first member and the straingauges of the second member are adopted if the other outputs are out ofa predetermined range.
 19. The 6-axis sensor according to claim 14,characterized in that the angular interval is 90 degrees.
 20. The 6-axissensor according to claim 19, characterized in that the operative bodiesare disposed in positive and negative directions on X and Y axes with anorigin being defined at the central point of the first diaphragm. 21.The 6-axis sensor according to claim 14, characterized in that theangular interval is 120 degrees.
 22. The 6-axis sensor according toclaim 14, characterized in that the strain gauges are disposed: at edgeportions of the operative bodies on a line extending between a centralpoint of a portion on the plane corresponding to the operative bodies,and the central point of the first diaphragm; at edge portions of theoperative bodies on a line perpendicular to the former line at thecentral point of the portion on the plane corresponding to the operativebodies; and at either of edge portions of the operative bodies and edgeportions of the first diaphragm, at positions arranged around thecentral point of the first diaphragm at regular angular intervals and atthe same distance from the central point.
 23. The 6-axis sensoraccording to claim 1, characterized in that each of the strain gauges ismade of a piezoresistance element.
 24. The 6-axis sensor according toclaim 1, characterized in that each of the strain gauges is made of athin film of chromium oxide formed on an insulating film.